Fragile Post-Summer Cease-Fire Holds in Ukraine Amid Tensions with Moscow by Nathan Hodge

Ukrainian officials and Russian-backed separatists say a tenuous cease-fire has held for a week along the front lines in eastern Ukraine, after months of intense combat over the summer.

While the shaky cease-fire has held, both sides accuse the other of frequent violations, and exchanges of fire continue at contested points. And major Russian military drills along Ukraine’s border have heightened alarm in Kiev amid continuing Washington-Moscow tensions.

It is in that fraught context that Russia is carrying out large-scale military exercises in its Southern Military District. The drills, dubbed Caucasus-2016, involve around 12,500 troops, and include aviation assets and ships from Russia’s Black Sea and Caspian Sea fleets.

Some of the exercises are taking place around the Black Sea peninsula of Crimea, which Russia annexed from Ukraine in 2014, prompting swift condemnation by many nations, including the U.S. and its European allies. Defense analysts have noted a buildup of Russian forces inside Crimea in recent months, along with the deployment of additional troops to newly built installations along Ukraine’s border.

Underscoring those tensions, the Pentagon said Wednesday a Russian Su-27 fighter jet buzzed a U.S. Navy P-8A Poseidon surveillance aircraft in international airspace over the Black Sea, at one point closing to within 10 feet of the U.S. aircraft, according to U.S. officials.

The confrontation also comes amid frosty relations between Washington and Moscow, along with U.S. concern that Russian hackers are targeting U.S. electoral systems. U.S. President Barack Obama discussed Ukraine with Mr. Putin at the Group of 20 major economies this past weekend in China; the U.S. president described the discussion on Ukraine as constructive but not conclusive.

In a recent analysis, Kathleen Weinberger of the Institute for the Study of War said Mr. Putin doesn’t outright seek war with Ukraine, but “intends, rather, to use this mobilization and escalation of conflict to create leverage to weaken EU sanctions, destabilize the Ukrainian government, undermine NATO, and present the next American president with a series of faits accomplis.”